Electronic assemblies with high capacity heat sinks

ABSTRACT

An electronic assembly comprising one or more high performance integrated circuits includes at least one high capacity heat sink. The heat sink, which comprises a number of fins projecting substantially radially from a core, is structured to capture air from a fan and to direct the air to optimize heat transfer from the heat sink. The heat sink fins can be formed in different shapes. In one embodiment, the fins are curved. In another embodiment, the fins are bent. In yet another embodiment, the fins are curved and bent. Methods of fabricating heat sinks and electronic assemblies, as well as application of the heat sink to an electronic assembly and to an electronic system, are also described.

DIVISIONAL APPLICATION

[0001] The present application is a divisional of application U.S. Ser.No. 09/950,100, filed on Sep. 10, 2001.

RELATED APPLICATIONS

[0002] The present application is related to the following applicationswhich are assigned to the same assignee as the present application:

[0003] Ser. No. 09/716,510, now U.S. Pat. No. 6,633,484, entitled “HeatDissipating Devices, Systems, and Methods with Small Footprint”;

[0004] Ser. No. 09/766,757, now U.S. Pat. No. 6,535,385, entitled“High-Performance Heat Sink Configurations For Use In High DensityPackaging Applications”;

[0005] Ser. No. 09/800,120, entitled “Radial Folded Fin Heat Sink”;

[0006] Ser. No. 09/860,978, now U.S. Pat. No. 6,479,895, entitled “HighPerformance Air Cooled Heat Sinks Used In High Density PackagingApplications”;

[0007] Ser. No. 10/047,101, entitled “Heat Sinks and Methods ofFormation” (Client Docket P11461);

[0008] Ser. No. 09/950,898, entitled “A Manufacturing Process for aRadial Fin Heat Sink”);

[0009] Ser. No. 09/950,101, entitled “Radial Folded Fin Heat Sinks andMethods of Making and Using Same” (Attorney Docket 884.468); and

[0010] Ser. No. 10/656,968, entitled “Electronic Assemblies with HighCapacity Heat Sinks and Methods of Manufacture”.

TECHNICAL FIELD

[0011] The inventive subject matter relates generally to electronicspackaging and, more particularly, to several embodiments of anelectronic assembly that includes a high-performance electroniccomponent and a high capacity heat sink, and to manufacturing methodsrelated thereto.

BACKGROUND INFORMATION

[0012] Electronic components, such as integrated circuits (ICs), aretypically assembled into packages by physically and electricallycoupling them to a substrate, such as a printed circuit board (PCB), toform an “electronic assembly”. The “electronic assembly” can be part ofan “electronic system”. An “electronic system” is broadly defined hereinas any product comprising an “electronic assembly”. Examples ofelectronic systems include computers (e.g., desktop, laptop, hand-held,server, Internet appliance, etc.), wireless communications devices(e.g., cellular phones, cordless phones, pagers, etc.), computer-relatedperipherals (e.g., printers, scanners, monitors, etc.), entertainmentdevices (e.g., televisions, radios, stereos, tape and compact discplayers, video cassette recorders, MP3 (Motion Picture Experts Group,Audio Layer 3) players, etc.), and the like.

[0013] In the field of electronic systems there is an incessantcompetitive pressure among manufacturers to drive the performance oftheir equipment up while driving down production costs. This isparticularly true regarding the packaging of ICs on substrates, whereeach new generation of packaging must provide increased performance,particularly in terms of an increased number of components and higherclock frequencies, while generally being smaller or more compact insize.

[0014] As the internal circuitry of ICs, such as processors, operates athigher and higher clock frequencies, and as ICs operate at higher andhigher power levels, the amount of heat generated by such ICs canincrease their operating temperature to unacceptable levels, degradingtheir performance or even causing catastrophic failure. Thus it becomesincreasingly important to adequately dissipate heat from ICenvironments, including IC packages.

[0015] For this reason, electronic equipment often contains heatdissipation equipment to cool high-performance ICs. One known type ofheat dissipation equipment includes an impinging fan mounted atop a heatsink. The heat sink comprises a plurality of radial fins or rods formedof a heat-conductive material such as copper or aluminum formed around acore. The bottom surface of the core is in thermal contact with the ICto conduct heat from the IC to ambient air. The fan moves air over thefins or rods to enhance the cooling capacity of the heat dissipationequipment. However, with high-performance ICs consuming ever greateramounts of power and accordingly producing greater amounts of heat, heatdissipation equipment must have higher heat dissipation capability thanthat heretofore obtained.

[0016] In order to offer higher capacity heat transfer, new heatdissipation equipment must be more efficient. It is difficult forair-cooled heat sinks to grow in size, because equipment manufacturersare under tremendous competitive pressure to maintain or diminish thesize of their equipment packages, all the while filling them with moreand more components. Thus, competitive heat dissipation equipment mustbe relatively compact in size and must perform at levels sufficient toprevent high-performance components from exceeding their operationalheat specifications.

[0017] For the reasons stated above, and for other reasons stated belowwhich will become apparent to those skilled in the art upon reading andunderstanding the present specification, there is a significant need inthe art for apparatus and methods for packaging high-performanceelectronic components in an electronic assembly that minimize heatdissipation problems.

BRIEF DESCRIPTION OF THE DRAWINGS

[0018]FIG. 1 is a perspective view of a prior art electronic assemblyincluding a heat sink attached to an IC package;

[0019]FIG. 2 is a top view of a prior art radial fin heat sink;

[0020]FIG. 3 is a top view of the portion within dashed rectangle 22 ofFIG. 2, showing an air flow pattern within fins of a prior art radialfin heat sink;

[0021]FIG. 4 is a side view of a section, taken between dashed linesegments 24 and 25 of FIG. 2, of a prior art radial fin heat sinkpositioned upon an IC package;

[0022]FIG. 5 illustrates a perspective view of a curved fin heat sink,in accordance with an embodiment of the inventive subject matter;

[0023]FIG. 6 illustrates a top view of the curved fin heat sink shown inFIG. 5;

[0024]FIG. 7 illustrates a perspective view of an electronic assemblyincluding a curved fin heat sink positioned upon an IC package, inaccordance with an embodiment of the inventive subject matter;

[0025]FIG. 8 illustrates a perspective view of a portion of anelectronic assembly including an axial flow fan atop a curved fin heatsink, in accordance with an embodiment of the inventive subject matter;

[0026]FIG. 9 illustrates a top view of the portion within dashedrectangle 56 of FIG. 6, showing an air flow pattern within fins of acurved fin heat sink, in accordance with an embodiment of the inventivesubject matter;

[0027]FIG. 10 illustrates a side view of a section of the curved finheat sink shown in FIG. 6, taken between dashed line segments 51 and 53;

[0028]FIG. 11 illustrates a perspective view of a bent fin heat sink, inaccordance with an embodiment of the inventive subject matter;

[0029]FIG. 12 illustrates a top view of a bent fin heat sink, inaccordance with an embodiment of the inventive subject matter;

[0030]FIG. 13 illustrates a perspective view of an electronic assemblyincluding a bent fin heat sink positioned upon an IC package, inaccordance with an embodiment of the inventive subject matter;

[0031]FIG. 14 illustrates a schematic view of a fan, including itstangential and axial air flow components, and a side view of a bent finheat sink as positioned upon a sectioned IC package on a substrate, inaccordance with an embodiment of the inventive subject matter;

[0032]FIG. 15 illustrates a perspective view of a curved-bent fin heatsink, in accordance with an embodiment of the inventive subject matter;

[0033]FIG. 16 illustrates a top view of a curved-bent fin heat sink, inaccordance with an embodiment of the inventive subject matter;

[0034]FIG. 17 illustrates a perspective view of an electronic assemblyincluding a curved-bent fin heat sink positioned upon an IC package, inaccordance with an embodiment of the inventive subject matter;

[0035]FIG. 18 illustrates an air flow pattern for a prior art radial finheat sink;

[0036]FIG. 19 illustrates an air flow pattern for a bent fin heat sink,in accordance with an embodiment of the inventive subject matter;

[0037]FIG. 20 illustrates an air flow pattern for a curved-bent fin heatsink, in accordance with an embodiment of the inventive subject matter;

[0038]FIG. 21 illustrates a flow diagram of a method of fabricating aheat sink, in accordance with an embodiment of the inventive subjectmatter;

[0039]FIG. 22 illustrates a flow diagram of a method of fabricating anelectronic assembly, in accordance with an embodiment of the inventivesubject matter; and

[0040]FIG. 23 is a block diagram of an electronic system incorporatingat least one electronic assembly with at least one high capacity heatsink, in accordance with an embodiment of the inventive subject matter.

DETAILED DESCRIPTION

[0041] In the following detailed description of some exemplaryembodiments of the inventive subject matter, reference is made to theaccompanying drawings which form a part hereof, and in which is shown byway of illustration, but not of limitation, some specific embodiments inwhich the inventive subject matter may be practiced, including apreferred embodiment. These embodiments are described in sufficientdetail to enable those skilled in the art to understand and practicethem, and it is to be understood that other embodiments may be utilizedand that structural, mechanical, compositional, and procedural changesmay be made without departing from the spirit and scope of the inventivesubject matter. The following detailed description is, therefore, not tobe taken in a limiting sense, and the scope of embodiments of theinventive subject matter is defined only by the appended claims. Suchembodiments of the inventive subject matter may be referred to,individually and/or collectively, herein by the term “invention” merelyfor convenience and without intending to voluntarily limit the scope ofthis application to any single invention or inventive concept if morethan one is in fact disclosed.

[0042] The inventive subject matter provides a solution to thermaldissipation problems that are associated with prior art packaging ofintegrated circuits that have high circuit density and that operate athigh clock speeds and high power levels, by employing a high capacityheat sink. Various embodiments are illustrated and described herein.

[0043] In one embodiment, the heat sink comprises a thermally conductivecore. The core has a number of thermally conductive fins projecting fromit in a substantially radial fashion. The core can have a central cavityinto which a thermally conductive material is inserted. The heat sinkfins can be formed in various shapes. In one embodiment, the fins arecurved. In another embodiment, the fins are bent. In yet anotherembodiment, the fins are curved and bent.

[0044] In one embodiment, the heat sink can be used in an electronicassembly having an impinging fan, e.g. an axial flow fan, directing aironto an upper face of the heat sink. The lower face of the heat sink isin thermal contact with a heat-generating electronic component such as ahigh performance IC. The heat sink is structured to capture air from thefan and to direct the air to optimize heat transfer from the heat sink.

[0045] Various methods of fabricating heat sinks and electronicassemblies are also described.

[0046]FIG. 1 is a perspective view of a prior art electronic assembly 1including a heat sink 2 attached to an IC package 5. Electronic assembly1 comprises a plurality of electronic components 5-9 mounted upon aprinted circuit board (PCB) 3. Heat sink 2 comprises a relatively thick,flat base plate 12 and an array of fins 11 extending to the edge of andsubstantially perpendicular to the base plate 12. Although the fins 11shown in FIG. 1 are folded fins, other prior art heat sinks do not havefolded fins. For example, it is known in the prior art to use brazed,machined, or extruded solid fins. Base plate 12 is clamped to IC package5 through an attachment device 13. Base plate 12 is often formed ofsolid copper, and it contributes a significant amount of cost and massto electronic assembly 1.

[0047] While the sizes of packaged, high performance ICs are decreasing,the amount of heat generated by these components per unit volume isincreasing. Increasing the heat dissipation capabilities of the priorart heat sink 2 would require enlarging the surface area of the baseplate 12 and/or the array of fins 11. This in turn would result inconsuming more PCB real estate, which is generally not a viable optionin an environment where system packaging densities are increasing witheach successive, higher performance, product generation.

[0048] Prior art heat sink 2 illustrated in FIG. 1 can be used inconjunction with an axial flow fan (not shown in FIG. 1) to increaseheat dissipation from the array of fins 11. An axial flow fan has aspinning impeller that is generally shaped like an airfoil. Onecomponent of the air flow emanating from an axial flow fan movesparallel to the axis about which the impeller rotates, and this “axialcomponent” is directed normal to the array of fins 11 of the heat sink2, i.e. perpendicular to the PCB 1. (Refer to axial component 132 inFIG. 14.)

[0049] Another component of the air flow from an axial flow fan istangential to the impeller's direction of rotation. This “tangentialcomponent” results in air swirling about the impeller's axis ofrotation. (Refer to tangential component 130 in FIG. 14.) The ratio ofair being moved by the axial component versus the tangential componentvaries with the particular fan blade geometry. For example, low anglesof attack in the fan blade generally result in a higher ratio of axialflow, while high angles of attack generally result in a higher ratio oftangential flow. In some axial flow fans, the ratio is 1:1.

[0050] When an axial flow fan is mounted facing downward on prior artheat sink 2, its axial component of air flow provides substantially allof the cooling effect, because very little of the tangential componentof air flow is captured by the straight vertical fins 11.

[0051]FIG. 2 is a top view of a prior art radial fin heat sink 20. Heatsink 20 is referred to as a “radial fin heat sink”, because its fins 21emanate radially from a central core 41. Fins 21 are substantiallystraight, and the base of each fin 21 is attached to core 41 parallel toa central axis 42 (refer to FIG. 4). Referring back to FIG. 2, core 41can have a central cavity 23, and a thermal plug 40 of thermallyconductive material can reside within cavity 23 to enhance thermaldissipation.

[0052]FIG. 3 is a top view of the portion within dashed rectangle 22 ofFIG. 2, showing an air flow pattern within fins of the prior art radialfin heat sink 20 shown in FIG. 2. In FIG. 3, a tangential air flowcomponent 29 from an axial flow fan (not shown) impinges upon fins 26and 27.

[0053] Before discussing tangential air flow component 29, it should befirst noted that fins 26 and 27 are substantially perpendicular to core41, and that fins 26 and 27 diverge considerably as they emanate fromcore 41. The radius 43 at the base of fins 26 and 27 is substantiallysmaller than the fin tip distance 28 at the tips of fins 26 and 27.

[0054] Tangential air flow component 29 impinges against the fins ofprior art radial fin heat sink 20, such as fins 26 and 27. A majorportion 30 of tangential air flow component 29 moves outwardly towardsthe tips of fins 26 and 27. A smaller portion 33 of tangential air flowcomponent 29 moves inwardly towards the bases of fins 26 and 27.

[0055] Due to the diverging geometry of fins 26 and 27, air flow fromthe tangential component 29, as well as air flow from the axialcomponent (not seen in FIG. 3), moves towards the fin tips to escape theregion between adjacent fins 26 and 27, and thus little air flow reachesthe hottest part of fins 26 and 27 near core 41. This results ininefficient thermal dissipation. Consequently, a more powerful andnoisier fan must be substituted, or the electronic component will not besufficiently cooled to avoid performance degradation or catastrophicfailure.

[0056]FIG. 4 is a side view of a section, taken between dashed linesegments 24 and 25 of FIG. 2, of a prior art radial fin heat sink 20positioned upon an IC package 34. Fins 31 and 32 are on opposite sidesof heat sink 20. The lower surface of thermal plug 40 is in thermalcontact with the upper surface of a heat-producing IC package 34. Heat,represented by arrows 35, is transferred from IC package 34 into thermalplug 40. From thermal plug 40, heat is transferred through sidewall 38of cavity 23 to fin 31 (the heat sink core has been omitted to simplifythis illustration), and through sidewall 39 of cavity 23 to fin 32. Thehottest part of fins 31 and 32 is nearest the thermal plug 40.

[0057] A group 36 of air flow vectors is schematically shown torepresent an axial air flow component produced by an axial flow fan (notshown) downward between adjacent fins, including fin 31, of prior artradial fin heat sink 20. It will be seen that little if any air flowmoves against the hottest part of fin 31 nearest thermal plug 40.

[0058] Likewise, another group 37 of air flow vectors represents anaxial air flow component produced by the axial flow fan (not shown)downward between adjacent fins, including fin 32. Again, little if anyair flow moves against the hottest part of fin 32 nearest thermal plug40.

[0059] In addition, it is not readily apparent from FIGS. 3 and 4, butonly an insubstantial amount of air flow from the tangential componentproduced by a typical axial flow fan is captured by the prior art radialfin heat sink. This is illustrated further below regarding FIG. 18.

[0060] It should be apparent that what is needed is a heat sinkstructure that significantly increases the amount of air impinging uponthe hottest part of the heat sink, and that significantly increases thevolume and velocity of air moving through the heat sink fins, includingsignificantly increasing the amount of the tangential component of anaxial flow fan that is captured by the heat sink.

[0061]FIG. 5 illustrates a perspective view of a curved fin heat sink50, in accordance with an embodiment of the inventive subject matter.Curved fin heat sink 50 comprises a plurality of cooling fins 52arranged about a core 55. Fins 52 are formed of a material having highthermal conductivity such as a thermally conductive metal. In oneembodiment, fins 52 are formed of aluminum; however, they could also beformed of copper or any other suitable thermally conductive metal ormetal alloy.

[0062] Core 55 has a central axis 58. Core 55 can optionally have acentral cavity 54 for insertion of a thermal plug (not shown). Each fin52 has a base and a tip. The base of each fin 52 is coupled to core 55substantially parallel to central axis 58. It will be seen from FIG. 5that the tips of fins 52 define the periphery of a face to face thecomponent (e.g. IC package 64, FIG. 7), and that the face comprisesinterfin openings in the form of spaces between individual fins 52. Eachfin 52 is curved in the same relative direction. As will be seen fromthe description below, the fins 52 of curved fin heat sink 50 are shapedto capture the tangential component of air from an axial flow fan (notshown in FIG. 5). Fins 52 are also shaped to direct a relatively largevolume and relatively high velocity of air flow to contact substantiallythe entire surface of each fin 52, including the hottest portion of eachfin 52 adjacent the core 55.

[0063]FIG. 6 illustrates a top view of the curved fin heat sink 50 shownin FIG. 5. An explanation will now be given as to how curved fin heatsink 50 is shaped in order to maximize the number of cooling fins 52 fora desired “semi-rectangular” shape of curved fin heat sink 50 whilemaintaining a substantially uniform aspect ratio among all of coolingfins 52. “Semi-rectangular” is defined herein to mean a geometricalfigure having four straight or slightly curved (either concave orconvex) sides that meet at comers that are perpendicular, rounded,and/or otherwise different from perpendicular.

[0064] A semi-rectangular shape was chosen for one embodiment of curvedfin heat sink 50, because that shape most closely matched the footprintof a high performance IC package on which curved fin heat sink 50 wasmounted. A further constraint on the shape of curved fin heat sink 50,in this embodiment, was a “keep-out area” on the circuit board aroundthe IC package, due to the necessity of mounting other components in thekeep-out area and of minimizing the overall physical size of the circuitboard.

[0065] The semi-rectangular shape of curved fin heat sink 50 can be seenin FIG. 6, in that curved fin heat sink 50 comprises two slightlyconvex-curved sides of length 61 and two slightly convex-curved ends oflength 62. Each side meets a respective end at a rounded corner such ascorner 57.

[0066] Fins 52 are fabricated, in one embodiment, through an extrusionprocess. By using an extrusion process, heat sinks can be made at asignificant savings in manufacturing costs as compared with a process,for example, in which fins are machined from a heat sink core, or brazedor soldered onto a heat sink core. Using high volume manufacturingtechniques, extrusions several feet long can be quickly formed and thencut into individual curved fin heat sinks, each having a plurality ofcurved fins and, optionally if desired, a central cavity to accommodatea thermal plug.

[0067] However, the extrusion process for curved fins is currentlysubject to several process constraints. One constraint is that forextruding aluminum, for example, the aspect ratio of a curved fin 52,i.e. the ratio of the length of a fin 52 to the average width of the gapbetween two adjacent fins 52, cannot exceed about 10:1 to 12:1. Anotherconstraint is that the radius at the base of the fins cannot be lessthan about 1.0 to 1.2 millimeters.

[0068] Yet another constraint is to provide as many fins 52 as possible(subject to the above-mentioned radius constraint), with each fin 52 aslong as possible (subject to the above-mentioned aspect ratioconstraint), in order to provide as great a total heat dissipationsurface as possible. In the situation where the heat sink is being usedto cool an IC, the heat dissipation from the heat sink must be at leastsufficient to maintain a junction temperature within the IC at or belowa predetermined maximum value.

[0069] In view of the above-mentioned process constraints, the core 55is shaped to substantially match the shape or footprint of curved finheat sink 50, which in the embodiment shown in FIG. 6 is asemi-rectangular shape. Thus, core 55 comprises two slightlyconvex-curved sides of length 71 and two slightly convex-curved ends oflength 72. Each side meets a respective end at a rounded comer such ascomer 77. As a result, the aspect ratio of fins 52 can be maintainedsubstantially uniform around the entire periphery of curved fin heatsink 50. Some variation in aspect ratio of fins 52 around the peripheryof curved fin heat sink 50 is acceptable, so long as the maximum aspectratio of approximately 10:1 to 12:1 is not exceeded for any fin 52. Itwill be understood that with advances in extrusion technology the upperend of the aspect ratio range can be expected to rise; however, the sameprinciples of the disclosure will nonetheless be applicable to heatssinks extruded with more advanced extrusion technology.

[0070]FIG. 7 illustrates a perspective view of an electronic assembly 60including a curved fin heat sink 50 positioned upon an IC package 64, inaccordance with an embodiment of the inventive subject matter. ICpackage 64 is shown mounted upon a circuit board 63, which can be ofsimilar or identical type to the prior art circuit board illustrated inFIG. 1; however, circuit board 63 can be of any type. The lower face ofcurved fin heat sink 50 is in thermal contact with IC package 64.

[0071] An axial flow fan 65 is shown schematically positioned over theupper face of curved fin heat sink 50. Fan 65 comprises a plurality offan blades or impellers 66 that rotate, in the direction indicated byarrow 68, about an axis 67 that is substantially perpendicular to theupper face of curved fin heat sink 50.

[0072] Because heat sink 50 is considerably less expensive to fabricate,and has considerably less mass, than the prior art heat sink 2illustrated in FIG. 1, electronic assembly 60 is more commerciallydesirable than the prior art electronic assembly 1 illustrated in FIG. 1

[0073]FIG. 8 illustrates a perspective view of a portion of anelectronic assembly including an axial flow fan 70 atop a curved finheat sink 50, in accordance with an embodiment of the inventive subjectmatter. Fan 70 comprises a plurality of curved blades 74 disposed aboutan axis 69 that is substantially perpendicular to the upper face ofcurved fin heat sink 50. Blades 74 are attached to a hub 84 that isdriven, in the direction of rotation indicated by arrow 75, by fan motor73. A hold-down mechanism 76 is used to clamp fan 70 and curved fin heatsink 50 to the upper surface of a heat-producing IC (not shown) on acircuit board (not shown) underlying curved fin heat sink 50.

[0074]FIG. 9 illustrates a top view of the portion within dashedrectangle 56 of FIG. 6, showing an air flow pattern within fins 81 and82 of curved fin heat sink 50, in accordance with an embodiment of theinventive subject matter. In FIG. 9, a tangential air flow component 79from an axial flow fan (not shown) impinges upon fins 81 and 82. Eachfin, such as fin 81 or 82, is curved towards, or faces, counter to thedirection of rotation 75 of fan blades 74 (FIG. 8).

[0075] Before discussing tangential air flow component 79, it should befirst noted that the base regions of fins 81 and 82 are substantiallyperpendicular to core 55. From their bases, fins 81 and 82 curvesubstantially away from the perpendicular. However, fins 81 and 82diverge only slightly as they emanate from core 55. The radius 78 at thebase of fins 81 and 82 is only slightly smaller than the fin tipdistance 88 at the tips of fins 81 and 82. This geometry providessignificantly improved air flow between fins 81 and 82. It provides amore constricted path towards the tips of the fins, thus retaining moreof the air flow between the fins, where it can dissipate heat from thefins.

[0076] Tangential air flow component 79 impinges against the fins ofcurved fin heat sink 50, such as fins 81 and 82. A relatively smallportion 80 of tangential air flow component 79 moves outwardly towardsthe tips of fins 81 and 82. A significantly larger portion 83 oftangential air flow component 79 moves inwardly towards the bases offins 81 and 82. Thus, significantly more air flow is directed towardsthe hottest part of heat sink, i.e. core 55 and particularly the baseportions of fins 81 and 82 near core 55. Because air flow is directedinwardly toward the core, in some embodiments a fan shroud, which wouldblock air flow from exiting out the tips of the fins, may be dispensedwith, thus offering significant cost, mass, and reliability advantages.

[0077]FIG. 10 illustrates a side view of a section of the curved finheat sink 50 shown in FIG. 6, taken between dashed line segments 51 and53. Fins 91 and 92 are on opposite sides of curved fin heat sink 50. Thelower surface of thermal plug 90 is in thermal contact with the uppersurface of a heat-producing IC package 94. Heat, represented by arrows95, is transferred from IC package 94 into thermal plug 90. From thermalplug 90, heat is transferred through sidewall 98 of cavity 54 to fin 91(the heat sink core has been omitted to simplify this illustration), andthrough sidewall 99 of cavity 54 to fin 92. The hottest part of fins 91and 92 is nearest the thermal plug 90.

[0078] A group 96 of air flow vectors is schematically shown torepresent an air flow component produced by an axial flow fan (notshown) downward between adjacent fins, including fin 91, of curved finheat sink 50 (FIG. 6). Still referring to FIG. 10, it will be seen thatsubstantially more air flow moves against the hottest part of fin 91nearest thermal plug 90 than in the prior art radial fin heat sink 20,as was discussed earlier regarding FIG. 4. The increase in air flow isproduced by the curved fin geometry, which not only curves the fins tocapture both the normal and tangential components of the air flow fromthe axial flow fan, but which also has an inter-fin space of nearuniform width to allow air to move down between the fins at a highervolume and higher speed than if the fins widened towards their tips, asin the prior art heat sink 20 shown in FIG. 2.

[0079] Still referring to FIG. 10, another group 97 of air flow vectorsrepresents an air flow component produced by the axial flow fan (notshown) downward between adjacent fins, including fin 92. Again,substantially more air flow moves against the hottest part of fin 92nearest thermal plug 90.

[0080] In addition, although it is not readily apparent from FIGS. 9 and10, a substantial amount of air flow from the tangential componentproduced by a typical axial flow fan is captured by the fins of curvedfin heat sink 50 (FIG. 6). This again is achieved by the curved fingeometry that curves the fins towards the tangential component of airflow.

[0081] Thus, the curved fin heat sink 50 (FIG. 6) significantlyincreases the amount of air impinging upon the hottest part of thecurved fin heat sink 50, and it significantly increases the volume andvelocity of air moving through the curved fin heat sink 50, includingsignificantly increasing the amount of the tangential component of anaxial flow fan that is captured by the curved fin heat sink 50.

[0082] In addition, an axial flow fan used in conjunction with curvedfin heat sink 50 can have a relatively low rotational speed, thuskeeping fan noise to a minimum, while nonetheless producing sufficientair flow to dissipate heat from a heat-generating component in anelectronic assembly.

[0083]FIG. 11 illustrates a perspective view of a bent fin heat sink100, in accordance with an embodiment of the inventive subject matter.Bent fin heat sink 100 comprises a plurality of cooling fins 102arranged about a core 105. Fins 102 are formed of a thermally conductivemetal. In one embodiment, fins 102 are formed of aluminum; however, theycould also be formed of copper or any other suitable thermallyconductive metal or metal alloy.

[0084] Core 105 has a central axis 101. Core 105 can optionally have acentral cavity 106 for insertion of a thermal plug (not shown). Each fin102 has a base and a tip. The base of each fin 102 is coupled to core105 substantially parallel to central axis 101.

[0085] Each fin 102 comprises a vertical portion 107 and an angledportion 108. The angled portion 108 of each fin 102 is bent in the samerelative direction. As will be seen from the description below, the fins102 of bent fin heat sink 100 are shaped to capture the tangentialcomponent of air from an axial flow fan (not shown in FIG. 11). They arealso shaped to direct a relatively large and relatively high velocityair flow to contact substantially the entire surface of each fin 102,including the hottest portion of each fin 102 adjacent the core 105.

[0086] According to one embodiment of a bent fin heat sink 100, afterforming (e.g. by extrusion) a plurality of straight unbent finsemanating radially from core 105, the upper portion of the heat sink 100is counterbored to produce a counterbore 104, in which part of the baseof each fin 102 is sheared from core 105 in the vicinity only of angledportion 108. This allows angled portion 108 of each fin 102 to be bentin a subsequent operation.

[0087] In one embodiment, the angle that the angled portion 108 of eachfin makes with the vertical portion 107 is approximately 150 degrees. Inother embodiments, different angles could be used, depending upon theair flow characteristics of the particular axial flow fan being used inconjunction with the bent fin heat sink.

[0088] Instead of counterboring the upper portion of heat sink 100, ahole saw or other tool could be utilized to make a groove in the upperportion of heat sink 100 of sufficient depth to enable the angledportion 108 of each fin 102 to be bent.

[0089] It will be noted that for certain fins in the “corner” regions ofbent fin heat sink 100, their upper tips 109 are slightly clipped to fitinto a desired “semi-rectangular” (as earlier defined) footprint.However, in other embodiments, such clipping could be omitted.

[0090]FIG. 12 illustrates a top view of a bent fin heat sink 100, inaccordance with an embodiment of the inventive subject matter. Bent finheat sink 100 is shaped in order to maximize the number of cooling fins102 for a desired “semi-rectangular” shape of curved fin heat sink 100.

[0091] The semi-rectangular shape of curved fin heat sink 100 can beseen in FIG. 12, in that curved fin heat sink 100 comprises twosubstantially straight sides of length 111 and two substantiallystraight ends of length 112. Each side meets a respective end at arounded corner such as comer 114.

[0092] Fins 102 are fabricated, in one embodiment, through an extrusionprocess. The extrusion process for bent fins is currently subject tobasically the same process constraints as for the curved fin heat sinkdescribed in FIG. 6, except that the aspect ratio of the fins 102 can beslightly greater than for curved fins, ranging up to approximately 14:1to 16:1.

[0093] In view of the fact that the fabrication of the angled portions108 of the fins 102 of bent fin heat sink 100 requires counterboring acounterbore 104, the shape of core 105 is maintained generally circularin the embodiment shown in FIG. 12. However, in another embodiment, theshape of core 105 could be semi-rectangular, as in the embodiment shownin FIG. 6.

[0094] The trimmed upper tips 109 of certain fins 102 near the cornersof heat sink 100 can be seen in FIG. 12.

[0095]FIG. 13 illustrates a perspective view of an electronic assembly120 including a bent fin heat sink 100 positioned upon an IC 124package, in accordance with an embodiment of the inventive subjectmatter.

[0096] IC package 124 is shown mounted upon a circuit board 122, whichcan be of similar or identical type to the prior art circuit boardillustrated in FIG. 1; however, circuit board 122 can be of any type.

[0097] An axial flow fan 125 is shown schematically positioned over bentfin heat sink 100. Fan 125 comprises a plurality of fan blades orimpellers 126 that rotate, in the direction indicated by arrow 128,about an axis 127 that is substantially perpendicular to the upper faceof bent fin heat sink 100. Bent fin heat sink 100, in this embodiment,comprises a thermal plug 123. Thermal plug 123 can be formed of anysuitable thermally conductive material. In one embodiment, thermal plug123 is made of copper; however, aluminum or a copper or aluminum alloycould also be used.

[0098]FIG. 14 illustrates a schematic view of a fan 135, including itstangential air flow component 130 and its normal air flow component 132,and a side view of a bent fin heat sink 100 as positioned upon asectioned IC package 150 on a substrate 160, in accordance with anembodiment of the inventive subject matter.

[0099] Fan 135 can be similar or identical to fan 70 shown in FIG. 8.Fan 135 is an axial flow fan having a plurality of fan blades 136,rotating in a direction indicated by arrow 138, and disposed about anaxis of rotation 137.

[0100] Fan 135, when rotating about axis 137, produces an air flow thatcan be analyzed as having two different components. A tangentialcomponent 130 comprises a plurality of angular vectors 131 generallyincreasing towards the fan blade periphery. An axial component 132comprises a plurality of downward vectors 133, again generallyincreasing towards the fan blade periphery.

[0101] Because the fins 102 of bent fin heat sink 100 are angledtowards, or face, the tangential component 130, a relatively greater airflow, represented by arrows 140, is captured and flows downward betweenfins 102, exiting in the direction of arrows 142 beneath bent fin heatsink 100.

[0102] Thermal plug 123 of bent fin heat sink 100 is in thermal contactwith an IC package 150. IC package 150, illustrated in cross-section,includes a die 154 mounted on a package substrate 152 and covered with alid or integrated heat spreader (IHS) 158. A thermal grease or phasechange material 156 can be used between die 154 and IHS 158. Likewise, athermal grease or phase change material (not shown) can be used, ifdesired, between IHS 158 and thermal plug 123. Some of the relativedimensions of the structures shown in FIG. 14 are exaggerated ordiminished, and they are not drawn to scale. For example, in a differentembodiment the thermal plug 123 could be as wide as IHS 150, with bentfin heat sink 100 accordingly widened to accommodate an IHS 150 of suchwidth.

[0103]FIG. 15 illustrates a perspective view of a curved-bent fin heatsink 200, in accordance with an embodiment of the inventive subjectmatter. Curved-bent fin heat sink 200 comprises a plurality of coolingfins 202 arranged about a core 205. Fins 202 are formed of a thermallyconductive metal. In one embodiment, fins 202 are formed of aluminum;however, they could also be formed of copper or any other suitablethermally conductive metal or metal alloy.

[0104] Core 205 has a central axis 201. Core 205 can optionally have acentral cavity 206 for insertion of a thermal plug (not shown). Each fin202 has a base and a tip. The base of each fin 202 is coupled to core205 substantially parallel to central axis 201. Each fin 202 is curvedbetween its base and its tip, and the curve of each fin 202 is towardsthe same relative direction. In the embodiment shown in FIG. 15, eachfin 202 is curved towards, or faces, a counterclockwise direction,opposite to the direction of rotation of an axial flow fan to be used inconjunction with heat sink 200.

[0105] Each fin 202 comprises a vertical portion 207 and an angledportion 208. The angled portion 208 of each fin 202 is bent in the samerelative direction. As will be seen from the description below, the fins202 of curved-bent fin heat sink 200 are shaped to capture thetangential component of air from an axial flow fan (not shown in FIG. 15but shown in FIG. 17). They are also shaped to direct a relatively largeand relatively high velocity air flow to contact substantially theentire surface of each fin 202, including the hottest portion of eachfin 202 adjacent to the core 205.

[0106] According to one embodiment of a curved-bent fin heat sink 200,after forming a plurality of curved unbent fins emanating substantiallyradially from core 205, for example using an extrusion process, theupper portion of the heat sink 200 is counterbored to produce acounterbore 204 in which part of the base (i.e. inner portion) of eachfin 202 is sheared from core 205 in the vicinity only of angled portion208. This allows angled portion 208 of each fin 202 to be bent in asubsequent operation.

[0107] In one embodiment, the angle that the angled portion 208 of eachfin makes with the vertical portion 207 is approximately 150 degrees. Inother embodiments, different angles could be used, depending upon theair flow characteristics of the particular axial flow fan being used inconjunction with the bent fin heat sink.

[0108]FIG. 16 illustrates a top view of a curved-bent fin heat sink 200,in accordance with an embodiment of the inventive subject matter.Curved-bent fin heat sink 200 is shaped in order to maximize the numberof cooling fins 202 for a desired “semi-rectangular” shape ofcurved-bent fin heat sink 200.

[0109] The semi-rectangular shape of curved-bent fin heat sink 200 canbe seen in FIG. 16, in that curved-bent fin heat sink 200 comprises twoslightly convex-curved sides of length 211 and two slightlyconvex-curved ends of length 212. Each side meets a respective end at arounded corner such as comer 214.

[0110] Fins 202 are fabricated, in one embodiment, through an extrusionprocess followed by a counterboring process and then a bending process.The extrusion process for curved-bent fins is currently subject tobasically the same process constraints as for the curved fin heat sinkdescribed in FIG. 6. For this reason, the core 205 is shaped tosubstantially match the shape or footprint of curved-bent fin heat sink200, which in the embodiment shown in FIG. 16 is a semi-rectangularshape.

[0111] Thus, core 205 comprises two slightly convex-curved sides oflength 231 and two slightly convex-curved ends of length 232. Each sidemeets a respective end at a rounded comer such as corner 234. As aresult, the aspect ratio of the fins can be maintained substantiallyuniform around the entire periphery of curved-bent fin heat sink 200.Some variation in aspect ratio of the fins around the periphery ofcurved-bent fin heat sink 200 is acceptable, so long as the maximumaspect ratio of approximately 10:1 to 12:1 is not exceeded for any fin.

[0112]FIG. 17 illustrates a perspective view of an electronic assembly220 including a curved-bent fin heat sink 200 positioned upon an ICpackage 224, in accordance with an embodiment of the inventive subjectmatter.

[0113] IC package 224 is shown mounted upon a circuit board 222, whichcan be of similar or identical type to the prior art circuit boardillustrated in FIG. 1; however, circuit board 222 can be of any type.

[0114] An axial flow fan 225 is shown schematically positioned overcurved-bent fin heat sink 200. Fan 225 comprises a plurality of fanblades or impellers 226 that rotate, in the direction indicated by arrow228, about an axis 227 that is substantially perpendicular to the upperface of curved-bent fin heat sink 200. Curved-bent fin heat sink 200, inthis embodiment, comprises a thermal plug 223.

[0115]FIG. 18 illustrates an air flow pattern 250 for a prior art radialfin heat sink. Straight, vertical, radially-attached fins 251 eachreceive an air flow vector 255 from an axial flow fan (not shown) abovethe heat sink. As mentioned earlier, an axial flow fan produces an airflow having both an axial component directed substantially perpendicularto the upper face of the heat sink, and a tangential component in thedirection of rotation of the fan blades.

[0116] In FIG. 18, substantially all of the tangential component 256 ofair flow vector 255 is deflected away from the opening between adjacentfins 251. The predominant component of air flow into the space betweenadjacent fins 251 is the axial component 257. However, a portion ofaxial component 257 is also deflected away and does not go betweenadjacent fins 251, due to the vertical geometry of the fins. For thisfin geometry, there is increased air pressure between the fins,resulting in reduced mass flow and decreased heat dissipationperformance.

[0117]FIG. 19 illustrates an air flow pattern 260 for a bent fin heatsink, in accordance with an embodiment of the inventive subject matter.Bent, radially-attached fins 261 each receive an air flow vector 265from an axial flow fan (not shown) above the heat sink.

[0118] In FIG. 19, substantially all of the tangential component of airflow vector 265 is captured by the angled portions 269 of fins 261 andgoes into the space between adjacent fins 261, including verticalportions 268, which are the hottest portions of fins 261. Only a smallcomponent 266 of the tangential component is deflected away. Inaddition, little of the axial component 267 is deflected away, as occurswith the heat sink fin geometry of the prior art straight, radial finheat sink illustrated in FIG. 18, and most of axial component 267 goesbetween adjacent fins 261.

[0119]FIG. 20 illustrates an air flow pattern 270 for a curved-bent finheat sink, in accordance with an embodiment of the inventive subjectmatter. Curved-bent, radially-attached fins 271 each receive an air flowvector 275 from an axial flow fan (not shown) above the heat sink.

[0120] In FIG. 20, substantially all of the tangential component of airflow vector 275 is captured by the angled portions 279 of fins 271 andgoes into the space between adjacent fins 271, including verticalportions 278, which are the hottest portions of fins 271. Only a smallcomponent 276 of the tangential component is deflected away. Inaddition, little of the axial component 277 is deflected away, as occurswith the heat sink fin geometry of the prior art straight, radial finheat sink illustrated in FIG. 18, and most of axial component 277 goesbetween adjacent fins 271.

[0121] In addition, the curvature of fins 271 assists in directing theair flow inward towards the heat sink core (not shown, but in this viewit would be behind fins 271). Because substantial air flow from the fan(not shown) is captured by the curved-bent heat sink, and because thecaptured air flow is directed inward towards the heat sink core and thehottest part of fins 271 (next to the core), the curved-bent heat sinkis capable of dissipating a significant amount of heat from aheat-producing electronic component with which it is used.

[0122] In summary, for the fin geometries of the bent fin heat sink andthe curved-bent fin heat sink, there is decreased air pressure betweenthe fins, resulting in increased mass flow and increased heatdissipation performance.

[0123]FIG. 21 illustrates a flow diagram of a method of fabricating aheat sink, in accordance with an embodiment of the inventive subjectmatter. The method begins at 300.

[0124] In 302, a billet of thermally conductive metal, such as aluminumor copper, is obtained.

[0125] In 304, a plurality of fins are formed from the billet, forexample by an extrusion or micro-forging process. The fins extendoutwardly from a core in an asymmetric pattern (in the case of curvedfins). The core has a central axis, and each fin has a base that iscoupled to the core substantially parallel to the central axis. Ifdesired, a central cavity can be formed in the core. The central cavitycan be formed in any suitable manner, for example as part of theextrusion operation.

[0126] In 306, if the fins are to be bent, the process goes to 308;otherwise, it goes to 312.

[0127] In 308, the portions of the fins to be bent are separated fromthe core, for example by forming a cavity (e.g. by counterboring) orchannel (e.g. by machining or sawing) into the core a predetermineddistance along the central axis, from the top of the heat sink.

[0128] In 310, a portion of each fin is bent in substantially the samerelative direction. In one embodiment, the upper portion of each fin isbent down approximately 30 degrees from vertical, so that the angledportion of the fin forms an angle of approximately 150 degrees with thevertical portion of the fin.

[0129] In 312, which is optional depending upon whether a central cavitywas formed in 304, a thermal plug is inserted into the central cavity toprovide increased thermal dissipation from the IC through the heat sinkcore to the heat sink fins. The process ends at 314.

[0130]FIG. 22 illustrates a flow diagram of a method of fabricating anelectronic assembly, in accordance with an embodiment of the inventivesubject matter. The process begins at 400.

[0131] In 402, an electronic component is mounted on a circuit board.

[0132] In 404, an axial flow fan is provided. The axial flow fan iscapable of moving air having a component normal to the electroniccomponent and a component tangential to the electronic component.

[0133] In 406, a heat sink is mounted between the electronic componentand the axial flow fan. The heat sink includes a number of cooling finsthat are arranged about a core having a central axis. Each cooling finhas a base coupled to the core substantially parallel to the centralaxis. The cooling fins are shaped to capture both components of air,i.e. the axial component and the tangential component. A first face ofthe heat sink is in thermal contact with the electronic component andhas a semi-rectangular periphery. A second face of the heat sink facesthe fan and has a semi-rectangular periphery. The second face issubstantially opposite the first face. The core is shaped to maximizethe number of cooling fins while maintaining a substantially uniformaspect ration in the cooling fins. The method ends at 408.

[0134] The operations described above with respect to FIGS. 21 and 22could be performed in a different order from those described herein.Also, although the flow diagrams of FIGS. 21 and 22 are shown as havinga beginning and an end, they can be performed continuously.

[0135]FIG. 23 is a block diagram of an electronic system 501incorporating at least one electronic assembly 502 with at least onehigh capacity heat sink, in accordance with an embodiment of theinventive subject matter. Electronic system 501 is merely one example ofan electronic system in which embodiments of the inventive subjectmatter can be used. In this example, electronic system 501 comprises adata processing system that includes a system bus 504 to couple thevarious components of the system. System bus 504 provides communicationslinks among the various components of the electronic system 501 and canbe implemented as a single bus, as a combination of busses, or in anyother suitable manner.

[0136] Electronic assembly 502 is coupled to system bus 504. Electronicassembly 502 can include any circuit or combination of circuits. In oneembodiment, electronic assembly 502 includes a processor 506 which canbe of any type. As used herein, “processor” means any type ofcomputational circuit, such as but not limited to a microprocessor, amicrocontroller, a complex instruction set computing (CISC)microprocessor, a reduced instruction set computing (RISC)microprocessor, a very long instruction word (VLIW) microprocessor, agraphics processor, a digital signal processor (DSP), or any other typeof processor or processing circuit.

[0137] Other types of circuits that can be included in electronicassembly 502 are a chip set 507 and a communications circuit 508. Chipset 507 and communications circuit 508 are functionally coupled toprocessor 506, and they can be configured to perform any of a widenumber of processing and/or communications operations. Other possibletypes of circuits (not shown) that could be included within electronicassembly 502 include a digital switching circuit, a radio frequency (RF)circuit, a memory circuit, a custom circuit, an application-specificintegrated circuit (ASIC), an amplifier, or the like.

[0138] Electronic system 501 can also include an external memory 512,which in turn can include one or more memory elements suitable to theparticular application, such as a main memory 514 in the form of randomaccess memory (RAM), one or more hard drives 516, and/or one or moredrives that handle removable media 518 such as floppy diskettes, compactdisks (CDs), digital video disks (DVDs), and the like.

[0139] Electronic system 501 can also include a display device 509, oneor more speakers 510, and a keyboard and/or controller 520, which caninclude a mouse, trackball, game controller, voice-recognition device,or any other device that permits a system user to input information intoand receive information from the electronic system 501.

[0140] FIGS. 1-20 and 23 are merely representational and are not drawnto scale. Certain proportions thereof may be exaggerated, while othersmay be minimized. FIGS. 5-17, 19, 20, and 23 are intended to illustratevarious implementations of the inventive subject matter that can beunderstood and appropriately carried out by those of ordinary skill inthe art.

[0141] The inventive subject matter provides for a heat sink and anelectronic assembly that minimize thermal dissipation problemsassociated with high power delivery, and to methods of manufacturethereof. An electronic system and/or data processing system thatincorporates one or more electronic assemblies that utilize theinventive subject matter can handle the relatively high power densitiesassociated with high performance integrated circuits, and such systemsare therefore more commercially attractive.

[0142] By substantially increasing the thermal dissipation from highperformance electronic assemblies, such electronic equipment can beoperated at increased clock frequencies. Alternatively, such equipmentcan be operated at reduced clock frequencies but with lower operatingtemperatures for increased reliability.

[0143] As shown herein, the inventive subject matter can be implementedin a number of different embodiments, including a heat sink, anelectronic assembly, an electronic system, and various methods,including a method of fabricating a heat sink, and a method offabricating an electronic assembly. Other embodiments will be readilyapparent to those of ordinary skill in the art. The elements, materials,geometries, dimensions, and sequence of operations can all be varied tosuit particular packaging and heat-dissipation requirements.

[0144] While certain operations have been described herein relative to“upper” and “lower” surfaces, it will be understood that thesedescriptors are relative, and that they would be reversed if therelevant structure(s) were inverted. Therefore, these terms are notintended to be limiting.

[0145] Although specific embodiments have been illustrated and describedherein, it will be appreciated by those of ordinary skill in the artthat any arrangement that is calculated to achieve the same purpose maybe substituted for a specific embodiment shown. This application coversany adaptations or variations of the inventive subject matter.Therefore, it is manifestly intended that embodiments of this subjectmatter be limited only by the claims and the equivalents thereof.

What is claimed is:
 1. A heat sink for use with an axial flow fancomprising: a core having a central axis; and a plurality of coolingfins arranged about the core, each fin having a base and a tip, whereinthe bases are coupled to the core substantially parallel to the centralaxis, and wherein the fins are shaped to capture a tangential componentof air from the fan.
 2. The heat sink recited in claim 1, wherein anupper portion of each of the fins is bent towards the tangentialcomponent.
 3. The heat sink recited in claim 1, wherein the fins arecurved towards the tangential component, and wherein an upper portion ofeach of the fins is bent towards the tangential component.
 4. A heatsink for use with an axial flow fan comprising: a core having a centralaxis; and a plurality of cooling fins arranged about the core, each finhaving a base and a tip, wherein the bases are coupled to the coresubstantially parallel to the central axis, wherein the fins are shapedto capture a tangential component of air from the fan, and wherein thecore is shaped to maximize the number of fins while maintaining asubstantially uniform aspect ratio in the fins.
 5. The heat sink recitedin claim 4, wherein an upper portion of each of the fins is bent towardsthe tangential component
 6. The heat sink recited in claim 4, whereinthe fins are curved towards the tangential component, and wherein anupper portion of each of the fins is bent towards the tangentialcomponent.
 7. The heat sink recited in claim 4 wherein the corecomprises a central cavity to receive a thermal plug formed of amaterial having a high thermal conductivity.
 8. An electronic assemblycomprising: a substrate; an electronic component mounted on a surface ofthe substrate; an axial flow fan to move air towards the substrate, theair having an axial component and a tangential component; and a heatsink including a first face in thermal contact with the electroniccomponent; a second face facing the fan; a core having a central axis;and a plurality of cooling fins arranged about the core, each fin havinga base and a tip, wherein the bases are coupled to the coresubstantially parallel to the central axis, and wherein the fins areshaped to capture both components of air.
 9. The electronic assemblyrecited in claim 8, wherein an upper portion of each of the fins is benttowards the tangential component.
 10. The electronic assembly recited inclaim 8, wherein the fins are curved towards the tangential component,and wherein an upper portion of each of the fins is bent towards thetangential component.
 11. The electronic assembly recited in claim 8,wherein the electronic component comprises an integrated circuit (IC).12. The electronic assembly recited in claim 11, wherein the fins areformed of material having a high thermal conductivity, and wherein theaspect ratio of the fins is sufficient to maintain a junctiontemperature within the IC at or below a predetermined maximum value. 13.An electronic system comprising: a circuit board; a processor integratedcircuit (IC) mounted on the circuit board; at least one chipset mountedon the circuit board and electrically coupled to the processor IC foroperation in conjunction with the processor IC; at least one axial flowfan to move air towards the circuit board, the air having both an axialcomponent and a tangential component; and at least one heat sinkincluding a first face in thermal contact with either the processor ICor the chipset; a second face facing the at least one fan; a core havinga central axis; and a plurality of cooling fins arranged about the core,each fin having a base and a tip, wherein the bases are coupled to thecore substantially parallel to the central axis, and wherein the finsare shaped to capture both components of air.
 14. The electronic systemrecited in claim 13, wherein the core is shaped to maximize the numberof fins while maintaining a substantially uniform aspect ratio in thefins.
 15. The electronic system recited in claim 13, wherein the finsare formed of material having a high thermal conductivity, and whereinthe aspect ratio of the fins is sufficient to maintain a junctiontemperature within the IC at or below a predetermined maximum value. 16.The electronic system recited in claim 13, wherein the fins are curvedtowards the tangential component.
 17. The electronic system recited inclaim 13, wherein an upper portion of each of the fins is bent towardsthe tangential component.
 18. The electronic system recited in claim 13,wherein the fins are curved towards the tangential component, andwherein an upper portion of each of the fins is bent towards thetangential component.
 19. A heat sink comprising: a core having acentral axis, and having a surface to thermally contact aheat-generating electrical component; a plurality of cooling finsarranged about the core, each fin having a base and a tip, wherein thebases are coupled to the core substantially parallel to the centralaxis, and wherein an upper portion of each of the fins is bent in thesame relative direction; and a first face having a periphery defined bythe fin tips, wherein the first face is to face the component, andwherein the first face comprises inter-fin openings.
 20. The heat sinkrecited in claim 19, wherein the inter-fin openings extend from the baseto the tip of selected fins.
 21. The heat sink recited in claim 19,wherein the periphery of the first face has a semi-rectangular shape.22. The heat sink recited in claim 19, wherein the first facesubstantially matches the shape of the core.
 23. The heat sink recitedin claim 19, wherein the electronic component comprises an integratedcircuit (IC).
 24. The heat sink recited in claim 23, wherein the finsare formed of material having a high thermal conductivity, and whereinthe aspect ratio of the fins is sufficient to maintain a junctiontemperature within the IC at or below a predetermined maximum value. 25.A heat sink comprising: a core having a central axis, and having asurface to thermally contact a heat-generating electrical component; aplurality of cooling fins arranged about the core, each fin having abase and a tip, wherein the bases are coupled to the core substantiallyparallel to the central axis, wherein the fins are curved in the samerelative direction, and wherein an upper portion of each of the fins isbent; and a first face having a periphery defined by the fin tips,wherein the first face is to face the component, and wherein the firstface comprises inter-fin openings.
 26. The heat sink recited in claim25, wherein the inter-fin openings extend from the base to the tip ofselected fins.
 27. The heat sink recited in claim 25, wherein theperiphery of the first face has a semi-rectangular shape.
 28. The heatsink recited in claim 25, wherein the first face substantially matchesthe shape of the core.
 29. The heat sink recited in claim 25, whereinthe electronic component comprises an integrated circuit (IC).
 30. Theheat sink recited in claim 29, wherein the fins are formed of materialhaving a high thermal conductivity, and wherein the aspect ratio of thefins is sufficient to maintain a junction temperature within the IC ator below a predetermined maximum value.